﻿using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.IO;
using System.Linq;
using System.Web;

public class VerifyCode
{
    #region Private Fields 
    private const double PI = 3.1415926535897932384626433832795;
    private const double PI2 = 6.283185307179586476925286766559;
    //private readonly int _wordsLen = 4; 
    private int _len;
    private CodeType _codetype;
    private readonly Single _jianju = (float)18.0;
    private readonly Single _height = (float)24.0;
    private string _checkCode;
    #endregion
    #region Public Property 
    public string CheckCode
    {
        get
        {
            return _checkCode;
        }
    }

    #endregion

    #region Constructors 
    ///  
    /// public constructors 
    /// 
    /// 验证码长度  
    /// 验证码类型：字母、数字、字母+ 数字 、简单加法计算

    public VerifyCode(int len, CodeType ctype)
    {
        this._len = len;
        this._codetype = ctype;
    }
    public VerifyCode()
    {
        this._codetype = CodeType.Calc;
    }
    #endregion
    #region Public Field 
    public enum CodeType { Words, Numbers, Characters, Alphas, Calc }
    #endregion
    #region Private Methods

    public string GenerateNumbers()
    {
        string strOut = "";
        System.Random random = new Random();
        for (int i = 0; i < _len; i++)
        {
            string num = Convert.ToString(random.Next(10000) % 10);
            strOut += num;
        }
        return strOut.Trim();
    }

    public string GenerateCharacters()
    {
        string strOut = "";
        System.Random random = new Random();
        for (int i = 0; i < _len; i++)
        {
            string num = Convert.ToString((char)(65 + random.Next(10000) % 26));
            strOut += num;
        }
        return strOut.Trim();
    }
    public string GenerateCalc(out string result)
    {
        string strOut = "";
        System.Random random = new Random();
        int firstNum = random.Next(100000) % 30;
        int secondNum = random.Next(100000) % 20;
        strOut = string.Format(" {0} + {1} = ", firstNum, secondNum);
        result = (firstNum + secondNum).ToString();
        return strOut;
    }
    public string GenerateAlphas()
    {
        string strOut = "";
        string num = "";
        System.Random random = new Random();
        for (int i = 0; i < _len; i++)
        {
            if (random.Next(500) % 2 == 0) num = Convert.ToString(random.Next(10000) % 10);
            else num = Convert.ToString((char)(65 + random.Next(10000) % 26));
            strOut += num;
        }
        return strOut.Trim();
    }
    private System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)
    {
        System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);
        // 将位图背景填充为白色 
        System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);
        graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);
        graph.Dispose();
        double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;

        for (int i = 0; i < destBmp.Width; i++)
        {
            for (int j = 0; j < destBmp.Height; j++)
            {
                double dx = 0;
                dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;
                dx += dPhase;
                double dy = Math.Sin(dx);
                // 取得当前点的颜色 
                int nOldX = 0, nOldY = 0;
                nOldX = bXDir ? i + (int)(dy * dMultValue) : i;
                nOldY = bXDir ? j : j + (int)(dy * dMultValue);

                System.Drawing.Color color = srcBmp.GetPixel(i, j);
                if (nOldX >= 0 && nOldX < destBmp.Width && nOldY >= 0 && nOldY < destBmp.Height)
                {
                    destBmp.SetPixel(nOldX, nOldY, color);
                }
            }
        }
        return destBmp;
    }
    #endregion
    #region Public Methods
    public Stream CreateCheckCodeImage()
    {
        string checkCode;
        string showContent;
        switch (_codetype)
        {
            case CodeType.Alphas:
                checkCode = GenerateAlphas();
                showContent = checkCode;
                break;
            case CodeType.Numbers:
                checkCode = GenerateNumbers();
                showContent = checkCode;
                break;
            case CodeType.Characters:
                checkCode = GenerateCharacters();
                showContent = checkCode;
                break;
            case CodeType.Calc:
                showContent = GenerateCalc(out checkCode);
                break;
            default:
                checkCode = GenerateAlphas();
                showContent = checkCode;
                break;
        }
        this._checkCode = checkCode;
        MemoryStream ms = null;

        if (showContent == null || showContent.Trim() == String.Empty) return null;
        Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling(showContent.Length * _jianju), (int)_height);
        Graphics g = Graphics.FromImage(image);
        try
        {
            Random random = new Random();
            g.Clear(Color.White);
            // 画图片的背景噪音线 
            for (int i = 0; i < 18; i++)
            {
                int x1 = random.Next(image.Width);
                int x2 = random.Next(image.Width);
                int y1 = random.Next(image.Height);
                int y2 = random.Next(image.Height);
                g.DrawLine(new Pen(Color.FromArgb(random.Next()), 1), x1, y1, x2, y2);
            }
            Font font = new System.Drawing.Font("Times New Roman", 14, System.Drawing.FontStyle.Bold);
            LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
            if (_codetype != CodeType.Words)
            {
                for (int i = 0; i < showContent.Length; i++)
                {
                    g.DrawString(showContent.Substring(i, 1), font, brush, 2 + i * _jianju, 1);
                }
            }
            else
            {
                g.DrawString(showContent, font, brush, 2, 2);
            }
            // 画图片的前景噪音点 
            for (int i = 0; i < 150; i++)
            {
                int x = random.Next(image.Width);
                int y = random.Next(image.Height);
                image.SetPixel(x, y, Color.FromArgb(random.Next()));
            }
            // 画图片的波形滤镜效果 
            if (_codetype != CodeType.Words) image = TwistImage(image, true, 3, 1);

            // 画图片的边框线 
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
            ms = new System.IO.MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
        }
        finally
        {
            g.Dispose();
            image.Dispose();
        }
        return ms;
    }
    #endregion
}
